In a direct in-cylinder fuel injection system, it is important to achieve and maintain acceptable atomisation of fuel delivered to an engine, as well as to inject the atomised fuel into a combustion chamber of the engine within a required time interval, in order to efficiently control fuelling to, and hence operation of, the engine.
Air assist fuel injection systems have been developed in an endeavour to accommodate such fuelling requirements. Examples of such air assist fuel injection systems are disclosed in U.S. Pat. No. 4,693,224 and RE 36768, both of which have been assigned to the Applicant and the contents of which are incorporated herein by way of reference.
It can, however, be difficult to achieve and maintain atomisation to an extent which provides optimal fuel droplet size, particularly at high fuelling rates. It is also important in direct in-cylinder fuel injection systems to prevent or at least minimise the formation of any carbon deposits on or adjacent the fuel delivery surfaces which may otherwise impede the shape and nature of the fuel spray delivered into the combustion chamber of the engine.
It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed.